<VV> RE: Ed's strange turbo behavior

[Jim Simpson]

I guess I need to chime in here regarding late turbo 
performance.  I've owned mine (a '66 Corsa coupe) since '68.  In 1970 
I was stationed in Idaho and had a chance to wind it out on I-15.  In 
those days, it was a brand new road and very lightly traveled.

With GR-70/14 tires on the rear -- the largest I could fit in the 
wheel wheels -- and the stock 3.55 rear, it would reach redline in 
fourth gear.  If you do the math, allowing for the larger tires, 
that's just on 120 mph.  And the engine was still pulling, but I felt 
that was fast enough.  The car was stable with the stock spoiler and 
slightly smaller front tires -- ER-70/14 if I recall correctly.  (For 
those of you who aren't familiar with the letter tire sizes, they 
were introduced in the late 60s and disappeared sometime around 1970 or so.)

More recently, post a major restoration, I instrumented the engine to 
see just what was going on with the boost, throttle position, and 
fuel/air ratio.  The engine is still basically stock with the only 
change being a 0.040" overbore.  The electronic pressure sensor -- 
good to a percent or two -- shows that the stock turbo and YH carb 
combo can produce about 11 psi at around 4,000 rpm in third and 
fourth gear.  (I'm using one of the Safeguard knock sensors, but it 
wasn't pulling back on the timing so the engine was running at about 
it's peak.)

Now if I could find a good source of slightly higher octane gas, I 
might be able to do a tad better tweaking timing and whatnot...

Oh, yes, this is a senior division car and is driven to the shows...

Jim Simpson, Group Corvair, '66 Corsa turbo coupe.